Though the idea that vaccines are linked to autism has been disproven by multiple studies, an increasing number of parents are sending their kids off to school without their required vaccines, citing fears over autism and other health problems. Now doctors are concerned that growing resistance to vaccination could lead to a comeback from a variety of retro illnesses they've already beaten.

The researcher who helped popularize the belief that vaccines cause autism has already been…
Read more Read more

A study conducted by the Associated Press found that in eight states more than 1 in 20 public school kindergarteners aren't getting all their shots, and more than half of all states have seen a rise in the rate of parents requesting exemptions for their kids. Parents can opt out if they have medical, religious, or in some states philosophical concerns about the vaccines. The practice is still rare, and most kids have had more than 20 shots by the time they start school. However, in certain areas as many as 20 to 50 percent of children aren't getting the shots their states requires.

Emory University epidemiologist Saad Omer says, "Vaccine refusers tend to cluster," and the rates were drastically different from state to state. The AP's review of kindergarten exemption rates from 2006-07 and 2010-11 found,

Alaska had the highest exemption rate in 2010-11, at nearly 9 percent. Colorado's rate was 7 percent, Minnesota 6.5 percent, Vermont and Washington 6 percent, and Oregon, Michigan and Illinois were close behind.

Since vaccines aren't 100 percent effective, if there's a disease outbreak among unvaccinated kids, it could put other children at risk too. Certain areas have seen outbreaks of whooping cough and measles, and though experts think it's unlikely to happen in the U.S., people are now coming down with polio and diphtheria in parts of the world where the diseases had been eliminated.

A recent study of Washington State doctors found that about 75 percent of pediatricians are regularly hearing requests from parents to use a alternative vaccination schedule. About 60 percent said they'd work with parents on changing the timetable for vaccination, though they're less likely to budge when it comes to shots for particularly dangerous diseases like diphtheria, tetanus, and pertussis. While doctors are sympathetic to parents concerns, they aren't willing to budge if parents insist on ignoring science and making decisions that put everyone's kids in danger.